(1) Field of the Invention
The present invention relates to a towed antenna system and more particularly, to a plunging towed antenna system.
(2) Description of the Prior Art
Submersible vehicles must occasionally communicate with surface ships, satellites, aircraft, and other platforms as part of their operation. In order to broadcast and receive radio transmissions, they must deploy a large antenna above the ocean surface. To maintain stealth, for example, the submarine must remain submerged during this deployment. There are several known ways to accomplish this.
According to one method of antenna deployment, an antenna is mounted to a mast that is incorporated into the submarine  sail. When the submarine needs to communicate, the mast is deployed from the submarine sail by extending the antenna to the ocean surface similar to the extension of a periscope.
Mast deployed or mounted antennas are associated with several problems. In a first example, mast antennas create a significant wake when deployed at moderate boat speeds. This wake can be easily detected with electromagnetic, infrared, and optical sensors. Consequently, ship speeds are limited when a mast antenna pierces the surface and a wake is created.
Utilizing another method of antenna deployment, a submersible vehicle can communicate with other platforms while submerged using a buoyant towed antenna. A buoyant towed antenna typically includes a buoyant body that is connected by a tether to a winch disposed on the submerged vehicle. The winch allows the submerged vehicle to deploy the buoyant towed antenna to the ocean surface allowing the submerged vehicle to communicate with other platforms, and then to retrieve the buoyant towed antenna when the communication has been completed. Known buoyant towed antenna systems, however, use a winch that cannot operate in a “freewheel” manner, i.e. the winch does not permit the spool to spin freely. Thus, the winch must be powered in either direction to deploy or reel the buoyant towed antenna in. 
Buoyant towed antennas do not create large wakes associated with mast antennas while being towed, however, when towed at moderate speeds, their dynamic interactions with surface waves and the tow cable cause buoyant towed antennas to occasionally plunge under the ocean surface, crash through ocean waves, violently pitch and yaw, and create water sprays. All of these high-speed motion effects interfere with the operation of the onboard electromagnetic communication devices.